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Old 05-23-2012, 07:21 AM   #1
Junior Member
Join Date: Apr 2012
Posts: 3
rv water pump losing prime

Hi all,

I just went through a battle finding the reason for my water pump losing prime. Here was the symptom.

You turn on a faucet and it takes about 30 to 45 seconds before it primes. You then shut it off and it comes to pressure and shuts off.
Now, you wait maybe 1 minute and turn it on and it has lost prime and takes about 30 seconds to reprime. I started to check from the intake backwards and resealed each connection one at a time and then retry.

Let me pause here:

We have a 2008 Jayco Melbourne 29D. It has a water distribution center for different choices, such as CITY WATER, CITY FILL, COUNTRY FILL, NORMAL OPERATION ETC.

I back tracked to the distribution manifold and found where the pump intake line was connected. It is a nylon nipple on one end to thread on the other and threads into a nylon female connection. I took this line off and unthreaded the nipple, put new teflon pipe thread tape on and reinstalled it. WOW!!!! Now it held prime. Even all night.

The hardest part was getting to the water pump area. Had to cut the control board in half and unscrew the panel that held the valving. Hope this will help someone somewhere. Remember the symptoms!!!

There could be other reasons for losing prime but with these symptoms, you know its a leak in the intake line sucking air and letting the water syphon back in the line.


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Old 05-24-2012, 06:19 PM   #2
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Posts: 1,183
Because of a lack of reply I will take a stab. Leak testing was part of my nondestructive testing job. I pressure test our system with compressed air (saves having to clean up after water squirts all over the place). This may mean plugging gravity fill and vent tube. If you can not find a hiss use a soapy solution and look for bubbles.

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Old 05-26-2012, 06:12 PM   #3
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Join Date: Oct 2011
Posts: 25

I had somewhat the same problem on my Jayco. It turn out to be the switch valve from tank to service water. There is a check valve built in to prevent water from backflowing.Best way to check it is hook up a hose like your camping somewhere. Turn water on then off. Disconnect hose and see if water drains from rv inlet.Good luck
2001 Jayco Eagle 283G v10
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